Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart of concern. Within the heart, the ability to control the exact position and orientation of the catheter tip is critical and largely determines how useful the catheter is.
A typical mapping or ablation catheter has an elongated catheter body, an intermediate deflectable section, a distal section carrying one or more electrodes, and a control handle in which the proximal end of at least one puller wire is anchored. The puller wire extends distally through the catheter body and at least through the intermediate deflectable section. A distal end of the puller wire is typically anchored at or near a junction of the deflectable section and the distal section. A compression coil surrounding the puller wire is generally provided through the catheter body, where a distal end of the compression coil defines an initiation location of the desired deflection. A protective tubing around the puller wire generally provided distal of the compression coil to protect the outer tubing of the catheter from being cut by the puller wire during deflection.
Unidirectional catheters use a single puller wire. Control handles for unidirectional catheter include control handles using a piston that is housed in a handle housing and longitudinally movable relative thereto for actuating the puller wire in achieving a desired deflection. Because the patient's heart is active with blood flow and moving walls and chambers, the catheter is subjected to forces that may cause the catheter to change or lose the deflection without an operator's constant attention and manipulation. Thus, the piston may have a friction-inducing member, for example, an O-ring, situated between the piston and the handle housing to maintain a desired deflection and prevent the piston from sliding or moving under these forces. However, the O-ring may not consistently provide sufficient friction to hold the piston and maintain the desired deflection.
Accordingly, it is desirable to provide a unidirectional catheter control handle with a tension mechanism that can releasably lock the piston in a particular position, and allow repositioning of the piston to a different position and adjusting of the amount of force needed to reposition the piston. Moreover, it is desirable that the mechanism allow control of the tension of deflection for providing a user with an enhanced ability to accurately position the catheter.